This invention relates generally to accumulation conveyors and, more particularly, to pneumatically actuated accumulation conveyors. The invention is especially adapted for use with belt-driven roller conveyors utilizing product detecting sensor rollers, but may be used with other drive systems and product detectors.
Pneumatically actuated accumulating conveyors have long been known. A commercially successful accumulation conveyor is disclosed in U.S. Pat. No. 3,768,630 issued to Russell A. Inwood et al. and assigned to the present assignee for an ACCUMULATOR WITH CONVEYOR OVERRIDE. The development of accumulation conveyors has evolved to the point where the units are reliable and controlled in a manner to optimize the throughput of product while providing the desired accumulation function. For example, in U.S. Pat. No. 5,191,967 issued to Bernard H. Woltjer and Arthur J. Terpstra, Jr., and assigned to the present assignee, for a CONVEYOR SYSTEM HAVING NON-SINGULATING ACCUMULATION CONVEYOR, the drive means of an associated zone is deactivated if the product sensing means for that zone and all of the product sensing means downstream of that zone sense the presence of product in order to produce an accumulation portion in which no zones are actuated. The drive means of an associated zone is actuated if any of the zones downstream of the associated zone are activated in order to produce a transport portion in which all zones upstream of any actuated zone are actuated to transport product without singulation of any upstream grouped product. The drive means for each zone is connected directly to the source of actuating fluid in order to actuate the drive means directly from the source.
It is further known to provide means to retract the sensing roller of a controlled zone when a zone downstream of that zone, with respect to product flow, is actuated resulting in actuation of that zone. This operation cascades upstream in the direction of product flow in order to retract the sensing rollers for all zones upstream of a zone whose sensing roller does not sense the presence of product in that zone. An improved accumulation conveyor with retractable sensor is disclosed in U.S. Pat. No. 5,358,097 issued to Douglas J. Bakkila et al. and assigned to the present assignee for an ACCUMULATION CONVEYOR WITH RETRACTABLE SENSOR. The accumulation conveyor disclosed in the Bakkila patent utilizes a retractable product sensor including an arm that is selectively positioned in the path of product being conveyed, a switch having an actuation member juxtaposed with the arm and a solenoid or cylinder that is responsive to actuation of the downstream zone actuator in order to apply a force to the switch and, in turn, retract the sensor. While such accumulation conveyor is especially useful for retrofit of existing accumulation conveyors, it requires separate hardware from that used with accumulation conveyors which do not have such retractable sensors. Furthermore, it may be desired to include sensing rollers which are not retractable interspersed with sensing rollers which are retractable which results in a further multiplication of sensor configuration.
Accumulation conveyors require an extensive inventory of components in order to accommodate various applications. Furthermore, each application must be individually engineered, which requires extensive engineering and drafting time. In addition to the engineering of each conveyor section, the integration of the accumulation conveyor sections with the rest of the conveyor system requires further extensive engineering effort. For example, the location of drive units must be coordinated not only with the rest of the conveyor system but with aisle ways for movement of personnel, lift trucks, and the like.
The known accumulation conveyors are not only difficult and time-consuming to engineers, but are also difficult to manufacture. Not only must extensive inventory of components be kept on hand, the assembly of those components requires the application of numerous fasteners, from different directions, which results in excessive assembly time. Furthermore, many of the components are assembled with poor tolerances which must be eliminated by subsequent adjustment of component positioning. This adds yet a further step in the manufacturing process and, hence, to the cost of the unit.
It is an object of the present invention to overcome the difficulties of the prior art and to provide an accumulation conveyor which is economical to engineer and build while being exceptionally functional and reliable in use.